1. Field of the Invention
The present invention generally relates to an active device, a pixel structure and a fabricating method thereof. More particularly, the present invention relates to a thin film transistor (TFT), a pixel structure having a high aperture ratio and a fabricating method thereof.
2. Description of Related Art
Nowadays, a multimedia technology has been well developed, which mostly benefits from the development of semiconductor devices and display apparatuses. As for displays, LCDs with the advantages such as high definition, favorable space utilization, low power consumption and non-radiation have gradually become the mainstream of the market.
In general, the LCD mainly includes an active device array substrate, a color filter substrate, and a liquid crystal layer sandwiched between the two substrates. FIG. 1A is a schematic view of a conventional active device array substrate, while FIG. 1B is a cross-sectional schematic view along line A-A′ in FIG. 1A. Referring to FIGS. 1A and 1B, a conventional active device array substrate 100 mainly includes a substrate 102, a plurality of scan lines 104, a plurality of data lines 106 and a plurality of pixel structures P1 (only one pixel structure P1 is depicted in FIG. 1A). The scan lines 104, the data lines 106 and the pixel structure P1 are all disposed on the substrate 102, and the pixel structure P1 is electrically connected to the scan line 104 and the data line 106.
In detail, the pixel structure P1 is mainly constituted by an active device 110 and a pixel electrode 120. The pixel electrode 120 may be electrically connected to the active device 110 through a contact window C1. It is known from FIG. 1B that the conventional active device 110 has a bottom gate structure and mainly includes a gate 110g, a gate insulating layer 110i, a channel layer 110c, an ohmic contact layer 110m, a source 110s and a drain 110d. In addition, a passivation layer 112 covers the active device 110 and has the contact window C1 exposing a part of the drain 110d. Thus, the pixel electrode 120 disposed on the passivation layer 112 may be electrically connected to the drain 110d through the contact window C1. During an actual operation, the active device 110 may be turned on by switching signals transmitted through the scan lines 104. After the active device 110 is turned on, display signals may be transmitted to the pixel electrode 120 through the data lines 106.
It should be noted that conductivity performance of the active device 110 is positively correlated to a length L and a width W of the channel layer 110c. To improve the conductivity performance of the active device 110, the length L and the width W of the channel layer 110c are increased, thus increasing the area occupied by the active device 110 on the substrate 102 and further reducing the aperture ratio of the pixel structure P1.